bathymetric surveying in lake superior: 3d modeling … · 2019-04-18 · and meet the modern...

BATHYMETRIC SURVEYING IN LAKE SUPERIOR: 3D MODELING AND SONAR

EQUIPMENTS COMPARING

E. Levin 1, G. Meadows 2, R. Shults 1, U. Karacelebi 1, H. S. Kulunk 1

1 Michigan Technological University, School of Technology, Townsend Drive, 1400 Houghton, 49931, USA, [email protected],

[email protected], [email protected], [email protected] 2 Michigan Technological University, Great Lakes Research Center, Townsend Drive, 1400 Houghton, 49931, USA,

[email protected]

Commission II, WGII/9

KEY WORDS: bathymetric surveying, autonomous underwater vehicles, sonar, seabed, profile.

ABSTRACT:

This paper represents the overview of hydrographic surveying and different types of modern and traditional surveying equipment, and

data acquisition using the traditional single beam sonar system and a modern fully autonomous underwater vehicle (AUV) IVER3.

During the study, the data sets were collected using the vehicles of the Great Lake Research Center at Michigan Technological

University. This paper presents how to process and edit the bathymetric data on SonarWiz5. Lastly, it compares the accuracy of the

two different sonar systems in the different missions and creates 3D models to display and understand the elevations changes. Moreover,

the 3D models were created after importing the data sets in the same coordinate system. In this study, the data sets were recorded by

two different sensors in the two study locations in the Keweenaw Waterway in Michigan, U.S. between the cities of Houghton and

Hancock. The first one equipment is the Lowrance HDS-7 sonar on the surveying boat, and other one is the EdgeTech 2205 sonar on

the fully AUV of IVER3. One of the purposes of this study is to explore the sonar post processing programs, which are very important

to interpret sonar and bathymetric data, and obtained the same coordinate system of the study areas. During the project, three main

processing programs were used. The first one is UnderSee Explorer 2.6, which has been used to process the data sets of Polar SV boat.

Secondly, EdgeTech Discover 4600 bathymetric software used EdgeTech 2205 sonar data sets to create bathymetric files that were

used in SonarWiz5. Lastly, SonarWiz5 sonar processing software can be used to process the data sets. After the data acquisition and

the data process, six profiles from the first study area and the five profiles from the second study are created to compare the data sets

and elevations difference. It is shown that single beam sonar might miss some details, such as pipeline and quick elevation changes on

seabed when we compare to the side scan sonar of IVER3 because the single side scan sonar can acquire better resolutions to understand

the 3D features, such as pipelines, reliefs etc.

1. INTRODUCTION

Hydrographic surveying is the measurement of the depth of water

bodies from the water surface and charting of the seafloor using

surveying measurements and sonar for navigation maps, marine

construction, offshore oil exploration and drilling, an underwater

pipeline, etc. Creating a bathymetric contour map is a design of

the depth of the seabed and shows lines of the same depth from

the coast. People have had a certain challenge to make these kinds

of maps. In land surveying, we can easily understand how

accurate we can measure unlike how we cannot see how accurate

we measure in the bathymetric survey. Underwater

measurements are the easy part because today’s sonars allow us

to obtain accurate distance in water. However, the problem is that

we might not know how far the survey boat is from the shoreline

or a control point when the measurement equipment records the

distance. Oceanographers have surveyed the seafloor and the

shape of the floor by using many tools. In today’s world though,

we use modern equipment, such as acoustic sonars, optical

systems, satellites, etc. They are much faster and more accurate

than ancient methods, so this equipment allows us to obtain a

better result. Hydrographic surveyors use sonar systems to

measure the distance from the seafloor or ocean floor. This

technique uses sound propagation to navigate and detect objects

from the surface vessels and underwater vehicles. Hydrographic

surveying is very significant for many countries’ economies

because many countries’ economies depend on waterways. For

instance, safe and efficient movement of goods through U.S.

ports is so important to develop the economy. According to the

Food and Agriculture Organization of the United Nations, more

than a billion tons of goods are shipped from all over the world

every year. Additionally, vacation vessels carrying nearly 10

million passengers departed U.S. ports in 2010, with the cruise

line industry accounting for $17 billion in direct spending in

2010. U.S. ports, a main part of the naval transportation system

might have the challenge of rising freight movements, so creating

a useful bathymetric contour map is very important to developing

countries' economies (NOAA, 2012).

Due to the strategic location of Lake Superior, which is the

largest of the Great Lakes of North America, it has an important

role in American history. It also has been a tactical commercial

waterway for people who live around the Great Lakes, so the U.S

government excavated many canals and connected many towns

using canal systems to transfer goods. So that, the hydrographic

surveying of that canals with an appropriate equipment and

software is a big challenge. Especially that task becomes hard in

a case of different software and equipment diversity.

2. RELATED WORKS

The research of different sonar equipment is a quiet common

question. The study are brought about by market of new devices

and software. Each year we have a deal with new models of sonar

systems and its combination with other measuring equipment e.g.

GNSS, IMU, laser scanning etc. (Moisan, et.al. 2015, Shia, et.al.

2017, Seube, et.al. 2017) and refined software. Another popular

direction of researches is a study of different sonar systems

opportunities for applied engineering tasks and environment

monitoring (Tassetti, et.al. 2015, Moisan, et.al. 2015, Wright,

et.al. 2016, Kulunk, 2017). Among these tasks, a special role has

underwater pipeline surveying and monitoring. That is why in

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-2/W10, 2019 Underwater 3D Recording and Modelling “A Tool for Modern Applications and CH Recording”, 2–3 May 2019, Limassol, Cyprus

This contribution has been peer-reviewed. https://doi.org/10.5194/isprs-archives-XLII-2-W10-101-2019 | © Authors 2019. CC BY 4.0 License.

101

mailto:[email protected]






our research we tried to compare different sonars and different

software for two areas, one of which has underwater pipeline.

Another feature of that area is abound of obstacles for GNSS

equipment, which in turn leads to additional problems with

positioning. We realize that different sonar systems namely

single-beam sonar and side-scan sonar have a different nature of

data capturing and data structure. In spite of that, the key feature

of our research to show in which circumstances and under which

conditions we can use this equipment.

3. HYDROGRAPHIC SURVEY EQUIPMENT

The hydrographic has various effects, and most of them are

related to the atmospheric and geographical conditions. All these

activities helped surveyors to obtain basic information of the

geographical and geophysical features of the seabed and coast.

The variation effects also give the information about the streams

and tides, but this data should be processed by proper techniques

and methods because it might have important influence on the

observation. Also, there is a relationship with the land and the

characteristics and dynamics of the seas and oceans (Emine,

2006). The variation effects are divided into four main parts:

- tidal variation and the influence of position;

- water quality and temperature;

- atmospheric effects;

- position accuracy.

These effects have to be accounted before surveying and

equipment choosing.

Today’s hydrographic survey equipment can accurately map a

sea floor and underwater topography using many different types

of equipment, such as multi beam, single beam, and side scan

sonar systems with the vessels’ positioning data.

Most survey vessels use multi beam and side scan sonars, which

use sound waves to measure depth to find and determine

underwater objects. The computer of the device accurately

measures the time of sound pulses from the sea bottom to its

receiver to compute the water depth. Some survey vessels also

use single beam echo sounders, split beam echo sounders, lead

lines, and some old fashion hydrographic survey equipment.

Moreover, more and more modern depth measurement

techniques are used to survey. For example, remote sensing,

aerial photogrammetry, and LIDAR (LIght Detection and

Ranging or Laser Imaging Detection and Ranging), which is a

remote sensing technology that can define underwater objects

and measure distances and water depth.

It is important to note that sonars are divided into two types,

active and passive sonars. Firstly, active sonars send a pulse of

sound into the water. This sound pulse hits an object and bounces

off the object and returns an echo to the transducer, which

receives signals to compute the power of the signal and to

determine the range and orientation of the object. Generally, this

sonar system can be used on submarines, AUV and Remotely

Operated Vehicles (ROV). It also can be towed near the survey

vessel at a fixed water depth (NOAA, 2014). Secondly, passive

sonar systems are mostly used to distinguish noise from

submarines, ships, and marine animals. It cannot emit its own

signal so the vessels, especially military vessels, want to use

passive sonars because they do not want to be found easily.

Moreover, passive sonars cannot measure the range of an object

without any other passive devices (NOAA, 2014).

One of the important missions is depth determination for

hydrographic surveys. It needs specific knowledge of underwater

acoustics, modern equipment, and sensors to achieve accuracy

and meet the modern hydrographic surveying standards.

Single Beam Sonar (SBS) systems have been very useful for the

bathymetric surveying (Fig. 1). These systems are less expensive

than other modern sonar equipment to map study areas. However,

they can obtain much less spatial resolutions when you compare

other modern equipment. Single beam sonars calculate the

double ways from the sonar receiver to sea floor using the

acoustic signals and sound velocity in water.

Figure 1. Single Beam Echo Sounder Principle (U.S. Geological

Survey Department of the Interior/USGS,

https://woodshole.er.usgs.gov/operations/sfmapping/singlebeam

.htm)

Multi beam echo sounders (MBES) is like single beam systems,

and it was designed that more beams are better than single beam

echo sounder. It also uses a single beam sonar way to measure

the underwater surface. The sound travels in water and bounces

off the underwater surface or other objects. The echo sounder can

measure and record the sound traveling time to compute the

depth. MBES generates so many soundings to completely cover

the surveying area. This surveying coverage area depends on the

depth of the surveying area. It usually covers two to four times

the water depth. Moreover, MBES can produce several acoustic

signals through a wide angular lateral aperture transducer, and

the sound travels in water and bounce off the underwater surface

or other objects. The reflection of sound echo is recorded to

compute the water depth using a wide band call swath (NOAA,

2018).

Side Scan Sonar (SSS) is a special sonar system that is used to

proficiently generate a large underwater image and detect the

objects on the underwater surface. Some of the side scan sonars

do not provide the bathymetry information. Also, this kind of

sonar can be used to design a map for the bathymetric missions

and surveying projects. It allows the users to understand the

texture type and shape of the underwater surface. This sonar

should be used together with the other sonars, such as single or

multi beam sonar systems to obtain full coverage of the surveying

area. Moreover, side scan sonars can be used to check the statues

of the underwater pipelines and cables, bathymetric surveying,

military operations and dredging applications. It is also very

useful in exploring mines and petroleum underwater.

Light Detection and Ranging (LIDAR) is one of the remote

sensing methods that can be used to measure the surveying places

using the form of a pulsed laser and GNSS receiver. It can

produce precise three dimensional information about a surveying

area quickly and easily. LIDAR devices are usually placed on

airplanes and helicopters to gain point clouds for traditional

topographic and bathymetric maps. This system is used to

establish water depths and shoreline elevations. It is important to



102

say that it is related to water clarity, but it can reach depths of 50

meters (NOAA, 2013).

4. STUDY AREAS AND DATA ACQUISITION

4.1 Study Locations

The study areas are at strategic locations between the cities of

Houghton and Hancock in the U.S. state of Michigan's Upper

Peninsula. In 1873, Houghton and Hancock gained a significant

position as a port when the Keweenaw Waterway was dredged

and extended from the Portage Lake, Portage Shipping Canal and

Lily in the Keweenaw Peninsula of Copper Island (Eckert, 1995).

Figure 2. The study areas are in Keweenaw Waterway map in

Michigan, USA including Houghton and Hancock (Base Map

From: NOAA Office of Coast Survey Public Domain)

Two study locations (Fig. 2) covers areas of approximately one

square km and depths between two and 15 m. The first study area

(Fig. 3) is on the pipeline between the cities of Hancock and

Houghton in Michigan and the dimensions of the surveying area

is approximately 0.9 square km (240 m x 340 m).

Figure 3. The Map of the First Study Area (Base Map From:

NOAA Office of Coast Survey Public Domain)

The second study area is located under the Portage Lake lift

bridge (Fig. 4), which is between Hancock and Houghton (Fig.

5)

Figure 4. Hancock-Houghton Lift Bridge

That area covers the surveying area of 0.15 square km.

Figure 5. The Map of the Second Study Areas (Base Map From:

NOAA Office of Coast Survey Public Domain)

4.2 Data Acquisition

The project field work was conducted by the Great lake Research

Center at Michigan Technological University and the study areas

were surveyed in the summer of 2015 using the ship of SV polar,

which is 22 feet surveying boat and has a Lowrance HDS-7 sonar

equipment, and AUV of IVER 3, which is a brand-new

equipment and has a EdgeTech 2205 modern digital side scan.

These two surveying vehicles surveyed two different study areas

and obtained two different data sets.

4.3 Data Processing

The data sets were processed on two different software to convert

raw surveying data, and to obtain usable information and produce

bathymetric surveying to create the models. In the process steps,

the raw GNSS navigations data were converted to the Michigan

State Plane Coordinate System, which is Michigan North Zone

2111 and UTM Zone 16 (Sickle, 2015). There are Undersee

Explorer 2.6 and SonarWiz5 sonar processing software used to

process the data sets. Moreover, EdgeTech Discover 4600

bathymetric software used Edge Tech 2205 sonar data sets to

create bathymetric files that were used in SonarWiz5. SV Polar

vehicle surveying data were processed on UnderSee Explorer

software, which uses a GNSS and sounder data to create high

definition bathymetry charts. Also, this software allows the

surveyors to import a sonar log file in real time with a computer.

In the Fig. 6, the software is shown.

Figure 6. UnderSee Explorer Software

It is important to say that this software is designed to be easy to

use. Receiving navigation positions, sounder positions and depth

data are instantly recorded and quickly processed to draw a

contour map on a computer screen in this real time mode and can

be quickly gathered and exported to your mission critical

applications.



103

EdgeTech’s software offers an approach to manage, accumulate,

and show bathymetry and side scan sonar data. These data sets

can be displayed on a color waterfall and be stored in the binary

EdgeTech JSF file format (EdgeTech Software 2013).

SonarWiz5 is the data procession and real time friendly sonar

data acquisition software that is designed for an all-in-one suite

of programs to meet your mapping standards, minimize project

cost and project time. It also helps the users to process your data

quickly and minimize the amount of software you need for the

surveying project. It has information about the side-scan and sub-

sonar equipment; therefore, the users do not need to set up many

complicated settings. It can be easily said that SonarWiz5 is easy

to use and can produce high quality results. Also, SonarWiz5 is

able to export in many different raster and vector format types,

such as sonar mosaics, digitized features, depth contours,

magnetometer contours, survey and others to Google Earth

KML/KMZ format (SonarWiz5 Software, 2013).

In this study, SonarWiz5 was used to process the IVER3 AUV

sonar data to get the bathymetric coordinates of the study areas.

During the study, the bottom tracking was provided to generate

better views to edit the data; it is also one of the steps to be done

before the signal processing and target recognizing.

5. STUDY RESULTS

5.1 Three Dimensional Views Creation

After the data acquisition and the data process, and editing the

data sets, SonarWiz5 Software was used to create the digital

elevations models of the study areas using more than 350,000

observations from AUV IVER3 sensor, and to display the three

dimensional surfaces using the interpolation method on

SonarWiz5. Moreover, the AutoCAD software was then used to

create the digital elevations models of the study areas using less

than 3,000 observations from the traditional beam sonar of the

Polar Boat, and to display the three dimensional surfaces on

AutoCAD. In addition, the six profiles from the first study area

and the five profiles from the second study were created to

compare the data sets of AUV IVER3 and Polar Boat's single

beam sonar. In this section, the quality of observations is in the

first order of Minimum Standard for Hydrographic Surveys

according the International Hydrographic Organization (IHO,

2005; IHO, 2008). However, it can be seen that the single beam

sonar might miss some details because of the sensor resolutions

and the way it uses. The side scan sonar can have better

resolutions and more dense points, which can be used for the

pipeline constructions or making a map for offshore petroleum

drilling or exploring projects.

Figure 7. Three Dimensional View of the First Study (the

Pipeline) Area Using the AUV IVER 3 Data on SonarWiz5

Furthermore, the two sonar sensors are compared, and explained

the positions errors because of the GNSS and multipath error and

missing details on the seabed because of the lack of observations

or interpolations. The surface models can be seen in the figures

below (Fig. 7 – Fig.10).

Figure 8. Three Dimensional View of the Second Study (Under

the Lift Bridge) Area Using the AUV IVER3 Data on

SonarWiz5

Figure 9. Three Dimensional View of the Second Study (Under

the Lift Bridge) Area Using the Polar Boat Data on AutoCAD

Carlson

Figure 10. Three Dimensional View of the First Study (the

Pipeline) Area Using the Polar Boat's Data on AutoCAD

Carlson

5.2 Compare the Data Sets

After creating the surface models, the six profiles and five

profiles are plotted to compare the difference of the observations

(Fig. 11).



104

Figure 11. The First and Second Study Area's Profiles

It also shows the missing details, such as holes or small bumps

on the surfaces.

Figure 12. The First Profile of the First Study Area

Figure 13. The Third Profile of the Second Study Area

Insofar as we do not have a precise 3D model of studied areas as

e.g. in (Débese, et.al. 2012), there is only way to check and

compare our data, it is profiles comparison. The some examples

of profiles for two study areas can be seen in the figures (Fig. 12

and Fig. 13) below, and the value of observations and RMS errors

can be seen in the table 1.

First Study Area (The Pipeline)

Profile's number RMS (m)

1 0.07

2 0.13

3 0.10

4 0.20

5 0.29

6 0.15

Second Study Area (The Lift Bridge)

1 0.11

2 0.11

3 0.21

4 0.10

5 0.21

Table 1. The RMS Errors of the Profiles

After comparison amongst eleven profiles, it is possible to make

some interesting conclusions.

6. CONCLUSION

In today’s world, hydrographic surveying is very important for

many countries’ economies because several countries’

economies depend on waterways, so safe and efficient movement

of goods through the ports is very significant to grow economies.

As a result of the economic reasons, obtaining bathymetric data

and making bathymetric charts are very important. People have

faced certain challenges to make these kinds of charts. This paper

presents the data acquisition using the traditional sonar system

and modern AUV, and processing their sonar and bathymetric

data sets on different surveying software. Lastly, it also compares

the accuracy of the two different sonar systems in the different

missions and creates three dimensional models to display and

understand the elevations changes. In this study, the data sets

were recorded by two different sensors in the two study locations

in the Keweenaw Waterway in Michigan, U.S. between the cities

of Houghton and Hancock during the summer of 2015. The first

one is the Lowrance HDS-7 sonar on the surveying boat, and

other one is the EdgeTech 2205 sonar on AUV of IVER3, which

have been rapidly becoming a significant vehicle in the

bathymetric surveying operations.

One of the purposes of this study was to explore the sonar post

processing programs, which are very important to interpret sonar

and bathymetric data. During the project, three main processing

programs were used. The first one is UnderSee Explorer 2.6,

which has been used to process the data sets of Polar SV boat.

Secondly, EdgeTech Discover 4600 bathymetric software used

EdgeTech 2205 sonar data sets to create bathymetric files that

were used in SonarWiz5. Lastly, SonarWiz5 sonar processing

software was used to process the data sets.

It can be said that these bathymetric surveying equipment and

software can be easily used in the missions,

- determining and observing shorelines, and underwater surface

- offshore oil exploration, offshore oil rigs and drilling

- pipeline and cable routing constrictions,



105

- creating charts for multipurpose

- marine construction, maritime navigation and dredging for

canals.

However, during the data acquisition, the observations had some

gross errors in depth because of the survey vessel and AUV

combine GNSS position with sonar equipment. One of the reason

of those errors for the second study area was measurements

accomplishment just under steel bridge. The bridge construction

led to multipath effect on GNSS. It can explain a high level of

blunders that were excluded from measurements using of three-

sigma rule before RMS calculation.

After the data acquisition and the data process, AutoCAD

software was used to create the digital elevations models of the

study areas, and to display the three dimensional surfaces.

Moreover, the six profiles from the first study area and the five

profiles from the second study were created to compare the data

sets and elevations difference of AUV IVER3 and Polar Boat's

single beam sonar. It is shown that single beam sonar might miss

some details, such as pipeline and quick elevation changes on

seabed when we compare to the side scan sonar of IVER3

because the single side scan sonar can acquire better resolutions

to understand the three dimensional features, such as pipelines,

reliefs etc. However, sometimes using single beam sonar can

save your project time and money because the single beam sonar

is cheaper than side scan sonars and the processing might be

easier than the side scan data.

ACKNOWLEDGEMENTS

Authors would like to say thank you for the opportunity given by

the Great Lake Research Center at Michigan Technological

University to carry out this research.

REFERENCES

Débese, N., Seube, N., Heydel, L. 2012. Qualitative and

quantitative description of multibeam echosounder systematic

errors on rocky areas, Marine Geodesy, VOL. 36, 306–321,

http://dx.doi.org/ 10.1080/01490419.2011.634963

Eckert, K.B., 1995. Buildings of Michigan (Society of

Architectural Historians), Oxford University Press, p. 461.

EdgeTech, 2013. Discover Bathymetric Acquisition Software

Manual, 1st ed: EdgeTech, 47 p.

Emine, O.G., 2006. Near Shore Bathymetric and Topographic

Survey in Marmara Sea, MSc Thesis, Bogazici University,

Turkey.

IHO, 2005. International Hydrographic Organization Manual on

Hydrography, International Hydrographic Bureau, May 2005,

1st ed., 46 p.

IHO, 2008. IHO Standards for Hydrographic Surveys, vol.

Special Publication No. 44, 5th Edition ed. MONACO:

International hydrographic Bureau, 36p.

Kulunk, H.S., 2017. Lakebed characterization using side-scan

data for investigating the latest Lake Superior coastal

environment conditions, MSc Thesis, Michigan Technological

University, US.

Moisan, E., Charbonnier, P., Foucher, P., Grussenmeyer, P.,

Guillemin, S., Koehl, M., 2015. Building a 3D reference model

for canal tunnel surveying using sonar and laser scanning, Int.

Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XL-5/W5,

153-159, https://doi.org/10.5194/isprsarchives-XL-5-W5-153-

2015

NOAA, 2012. Hydrographic Survey Priorities, Office of Coast

Survey, Available:

https://nauticalcharts.noaa.gov/publications/docs/national-

hydrographic-survey-priorities/nhsp-full%20document-

2012.pdf

NOAA, 2013. NOAA Technical Memorandum NOS CS 32 - A

procedure for developing an acceptance test for airborne

bathymetric lidar data application to NOAA charts in shallow

waters, Office of Coast Survey, 52 p., Available:

https://repository.library.noaa.gov/view/noaa/2645

NOAA, 2014. SONAR, Office of Coast Survey, Available:

http://oceanexplorer.noaa.gov/technology/tools/sonar/sonar.htm

l

NOAA, 2018. Hydrographic Specifications and Deliverables,

159 p., Office of Coast Survey, Available: https://nauticalcharts.noaa.gov/publications/docs/standards-

and-requirements/specs/hssd-2018.pdf

Seube, N Keyetieu, R. 2017. Multibeam echo sounders-IMU

automatic boresight calibration on natural surfaces, Marine

Geodesy, VOL. 40, NOS. 2–3, 172–186,

http://dx.doi.org/10.1080/01490419.2017.1310156

Shia, B., Lub, X., Yanga, F., Zhang, C., Lv, Y., Cheng, M. 2017.

Shipborne over- and under-water integrated mobile mapping

system and its seamless integration of point clouds, Marine

Geodesy, VOL. 40, NOS. 2–3, 104–122,

http://dx.doi.org/10.1080/01490419.2016.1272510

Sickle, J.V., 2015. GPS for Land Surveyors, 4th ed.: CRC Press,

349 p.

SonarWiz5, 2013. SonarWiz5 User Guide, California

Chesapeake Technology Inc., 791 p.

Tassetti, A. N., Malaspina, S., and Fabi, G. 2015. Using a

multibeam echosounder to monitor an artificial reef, In Proc. Int.

Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XL-5/W5,

207-213, https://doi.org/10.5194/isprsarchives-XL-5-W5-207-

2015

Wright, R.G., Baldauf, M. 2016. Hydrographic Survey in remote

regions: using vessels opportunity equipped with 3-dimensional

forward-looking sonar, Marine Geodesy, VOL. 36, 306–321,

http://dx.doi.org/10.1080/01490419.2011.634963



106

http://dx.doi.org/10.1080/01490419.2016.1272510

http://dx.doi.org/10.1080/01490419.2016.1272510

https://doi.org/10.5194/isprsarchives-XL-5-W5-153-2015






https://nauticalcharts.noaa.gov/publications/docs/national-hydrographic-survey-priorities/nhsp-full%20document-2012.pdf








http://oceanexplorer.noaa.gov/technology/tools/sonar/sonar.html




https://nauticalcharts.noaa.gov/publications/docs/standards-and-requirements/specs/hssd-2018.pdf




http://dx.doi.org/10.1080/01490419.2017.1310156

http://dx.doi.org/10.1080/01490419.2017.1310156

http://dx.doi.org/10.1080/01490419.2016.1272510

http://dx.doi.org/10.1080/01490419.2016.1272510





http://dx.doi.org/10.1080/01490419.2011.634963

http://dx.doi.org/10.1080/01490419.2011.634963

bathymetric surveying in lake superior: 3d modeling … · 2019-04-18 · and meet the modern...

Documents